Xinwei Sun

In order to adopt water electrolyzers as a main hydrogen production system, it is critical to develop inexpensive and earth-abundant catalysts. Currently, both half-reactions in water splitting depend heavily on noble metal catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. The efforts within this field for the discovery of efficient and stable earth-abundant catalysts (EACs) have increased exponentially the last few years. The development of EACs for the oxygen evolution reaction (OER) in acidic media is particularly important, as the only stable and efficient catalysts until now are noble-metal oxides, such as IrOx and RuOx. On the hydrogen evolution reaction (HER) side, there is significant progress on EACs under acidic conditions, but there are very few reports of these EACs employed in full PEM WE cells. These two main issues are reviewed, and we conclude with prospects for innovation in EACs for the OER in acidic environments, as well as with a critical assessment of the few full PEM WE cells assembled with EACs.

Polymer electrolyte membrane(PEM) fuel cells and electrolysers offer efficient use and production of H2 for emission-free transport and sustainable energy systems. In order to reduce the cost,complexity,flooding,catalyst poisoning and degradation,operation above 80°C and at lower relative humidities(RH) is preferable. Acid doped polybenzimidazole(PBI),sulfonated polyetheretherketone(SPEEK) and their composites are being investigated for high temperature and low RH operation with sufficient conductivities. We take a critical view and a surface protonic approach to gain fundamental insight.